Seems like a few other sharp minds have been thinking on the same lines. Here’s a post in the Financial Times discussing research on similar lines, but addressing impact of disruption by Brexit. Here’s their list of languages, though I recommend you read the full post:
In a globalising, automating world, a personal connect – the soft skills – will rise in value. There are few better ways to enhance your value, and the value of your experience than know the language of the people1.